Chastity Belt for Crusader's Wife

A brave Knight decided to join the Holy Crusades. Deciding that his wife must wear a chastity belt while he is gone, he locks up her nether regions and gives the key to his best friend.

He tells him, "If I don't return within 4 years, unlock my wife and set her free to live a normal life."

The husband leaves on horseback and about 20 minutes later, he sees a cloud of dust behind him.

He waits for it to come closer and sees it is his best friend, "What's wrong?" he asks.

"You gave me the wrong key!"